A non-active, hand-held surgical instrument designed to connect to a microwave ablation system generator to deliver microwaves to a targeted operative site for localized soft-tissue ablation, typically to treat tumours, hydatid cysts and/or menorrhagia. The probe includes a handle and a patient contact region (e.g., antenna, leaflets), and might include a cooling mechanism (via water irrigation). The device is intended to be used in percutaneous, endoscopic [e.g., gastroscopic, laparoscopic], natural orifice or open surgery procedures to ablate tissues (e.g., endometrial ablation). This is a single-use device.